Recently we decided to migrate away from our legacy reverse-proxy product to something that would integrate better with our AD \ Office 365 systems. I’ve wanted to try out Azure AD Application Proxy for a while since seeing it in beta last year so this seemed a good time to get to grips with it. This post outlines a few gotchas to watch out for and some useful background reading.

Let’s start off with the initial Microsoft documentation available here

Education freebies

Although Microsoft’s recent price hikes haven’t come at a good time for us in education we do get a lot of extras thrown into our Microsoft licensing agreement. One of the lesser-known ones is Azure AD Basic, which is the minimum requirement to use Azure AD Application Proxy – see comparison chart at https://www.microsoft.com/en-cy/cloud-platform/azure-active-directory-features for more info

To get your free licenses you’ll need to get in contact with your EES reseller and they’ll get them added to your tenant in a similar way to Office 365.

Applying the Azure AD Basic license is nice and simple, go to your Azure Management portal at https://manage.windowsazure.com, select your Azure AD directory then assign suitable groups to the license. What’s handy is that if you’re using Azure AD Connect to sync from your on-prem directory any new users will get automatically licensed as they come on board.

Installation

I used two dedicated Server 2012 R2 VMs for our install, the connector will be installed on each so we have failover should it be required at some point. Enabling the Application Proxy in Azure is nothing more than one click in the portal

Now in theory the installation should be straightforward, nothing more than downloading the installer from the link, sign in with admin credentials and job done. However if everything went that smoothly this blog wouldn’t exist (!)

Troubleshooting 403 Forbidden errors

At the end of the installation the wizard helpfully offers to run a troubleshooter to check all is well but in fact all was far from well…

Outbound firewall settings were already configured to allow all the ports that were asked for in the documentation, proxy was disabled in Connection Settings and the firewall didn’t register any outbound traffic being blocked so what’s going on here? The mystery deepens…

Although the wizard only offers to run the troubleshooter once you can run it again manually by launching it from:

Troubleshooting the troubleshooter

Although there’s a fair bit of documentation in the troubleshooting section on Microsoft’s pages none of it referred to this particular error. Google didn’t have much to go on either but did throw up some useful and detailed slides from the Ignite conference that are well worth a read:

Proxy proxy proxy!

However still no joy even with everything present as it should be. The next recommendation was to check if I was using a proxy server for outbound connections. We do have one but it’s not used for server VLANs and is the first thing I disable on a new VM build.

However I did get intrigued to check the traffic going out via TCPView… lo and behold there was the proxy server trying to take the outbound connections and failing miserably. It seems that despite everything in the operating system suggesting traffic should be going out directly the Connector was still trying to use the proxy route instead.

Checking Event Viewer and the Azure Portal afterwards showed success, my Connectors were now up and running with nice green icons, much better 🙂

Note: even though this fix resolves the issue the current version of the Troubleshooter doesn’t seem to follow the settings in the .config files and will still report connection failures. The Azure AD Application Proxy team are aware of this and are aiming to have a new version out soon.

Additional considerations

There’s a few other points to bear in mind when you’re completing the configuration of the application proxy. None of them are major issues but good to have everything ready before you start…

Certificates

Once the Connectors are up and running the rest of the process went smoothly, although note you will need a wildcard certificate if you want to publish your applications via a “vanity” URL i.e. your own domain rather than “msappproxy.net”

Using the vanity domain and some DNS CNAME records means that if you use Office 365 SharePoint for your Intranet your internal applications can work from the same URL both inside and outside.

Setting SPNs for Kerberos SSO

Even better, those internal apps can SSO based on the Office 365 initial sign-on for a suitably slick user experience! This does require a bit more configuration with Kerberos delegation but it’s not too bad.

When setting the SPN records I remembered the gotcha from when I worked on Dynamics CRM to type the command in manually… bizarre as it is the same still applies!

Nested groups

Finally, bear in mind if you’re using groups created natively in Azure AD you can’t nest memberships when creating application assignments, which is a shame. As a workaround create any nested ones in your local AD instead and sync them up via Azure AD Connect or just create flat groups in Azure AD if you prefer to work solely up there.

Application links

You can either publish your application links via your Intranet or users can browse them via the portal (I’ve linked to the new makeover version as it looks much better than the previous one in my opinion)

Making IT work

Welcome to my blog, my name is Gerrard Shaw, currently working as a Network Support Officer at Havering College of Further and Higher Education.

I'll be focusing on new developments with Office 365, Windows, Moodle and server \ networking technologies. I'm a great believer in sharing best practice and contributing to the wider technical community so hope you'll find something of interest...